The story is set in the Taisho Era at the beginning of the 20th century — except the era did not end in 15 years (as it did in real life) but lasted 25 years. To protect her family who fell from their former glory, a girl decides to marry a man whose name she does not even know. However, before she does, her little brother commits suicide in a mysterious fire, with an old book in hand.

The Imperial Library Information Assets Management Bureau — also known as "Fukurō" — then appears before the confused girl. According to the Fukurō, there exists books called Maremono, which exert a great influence on those who read it. Moreover, the girl gained the ability to see an "Aura" due to the incident with her brother. Despite her confusion, the girl chooses to leave the "birdcage" of her former life.